Annual or perennial herbs,
usually aromatic and glandular. Leaves alternate. Capitula
heterogamous, few-flowered, arranged on a receptacle in dense
hemispheric, ovoid or spherical clusters, which are terminal on
the stems and branches or in the axils of the leaves. Tips of the
bracts of the clusters and the bisexual florets usually purple. Subtending bracts of the capitula 2-4(-15),
sometimes forming a basal involucre. Bisexual florets in the
centre of the capitulum, fewer than the outer female florets.
Achenes ± cylindric or ellipsoid.
In this genus, the apparent
capitulum is in fact a cluster of capitula. Note - a similar
purple-flowered species with winged stems usually growing in marshy
places is Epaltes gariepina. Derivation of name: from sphaeros, a globe and antho, a flower, referring to the spherical form of the flower heads. Worldwide: 38 species in the Old World tropics, extending to Iran and Egypt Zimbabwe: 8 taxa. |
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